Engineering magnetic topological insulators in Eu-based Zintls

In Zintl materials, the rocksalt-like charge separation between the cationic and anionic frameworks offers a vital platform for the exploration of magnetic topological insulators. When the cations are magnetic and the anions are non-magnetic, it often causes the materials to behave as two independent subunits, with separate magnetic and electronic behaviors. In addition, the clear separation between the electronic and magnetic energy scales allows us to tune the electronic structure of the polyanionic network and then consider the effect of magnetism. This band engineering approach is achieved by employing doping, element substitution, pressure, and epitaxial strain. Specifically, starting from the trivial antiferromagnetic insulator Eu₅In₂Sb₆, we utilize density functional theory to engineer band inversions by applying chemical pressure via isoelectronic substitution, and use external pressure and epitaxial strain to control the bulk energy gaps. Our approach results in the prediction of three new antiferromagnetic topological insulator candidates: Eu₅Ga₂Sb₆, Eu₅Tl₂Sb₆, and Eu₅In₂Bi₆.